It is clear that the greatest impact of the HIV/AIDS epidemic is international, affecting above all middleand low-income countries in the developing world. And community-based research, regardless of its geography, has shown that effective collaboration among relevant stakeholders increases research relevance and efficacy and sustainability of interventions. Confronting AIDS with a community perspective and focus must thus be a key priority in any meaningful research response to the epidemic. The Global Community Core (GCC) will provide leadership and expertise to ensure that HIV Center research reflects actual "needs on the ground" in terms of both the US and international epidemics. It will coordinate and serve as an ongoing resource for the development of community-relevant global research by identifying emerging issues of significance in international and collaborative research, and fostering and sustaining collaborative relationships with partners at multiple levels (e.g., community, institutional, governmental) in every location where the Center conducts research. The Core will build upon existing partnerships and promote new ones to facilitate rigorous collaborative HIV-behavioral research, with a special emphasis on the large new programs (and funding mechanisms) that are transforming the landscape of HIV treatment, care, and prevention in the developing world - many of which are active at our home institution of Columbia University and elsewhere in New York City. Since the formation and maintenance of successful partnerships requires a thorough understanding of the diverse interests of stakeholders and of local contexts, the GCC will assist HIV Center investigators to create and sustain community partnerships at the local, state, national, and international levels, drawing on the community-based participatory research model. In the context of widespread "scale-up" of treatment with new opportunities for prevention, the GCC will also facilitate collaborations among scientists, policymakers, funders, health practitioners, community members, and other stakeholders in all settings, be they domestic or international. The Core will enhance the expertise of investigators as they move into new and more diverse settings, cross-nationally and cross-culturally. The GCC is committed to bringing tools, resources, expertise, and access to the global communities most affected by HIV/AIDS and to use treatment initiatives to enhance prevention opportunities at multiple levels of social organization, including the individual, family, community, health care institutions, community organizations, and government agencies